Sudden (and usually immediate) death due to impact to the chest (a phenomenon known as commotio cordis) in the absence of underlying cardiac disease has occurred in at least 170 documented cases. The object that initiates commotio cordis generally travels at a speed greater than 25 miles per hour when it strikes the person, which initiates instantaneous ventricular fibrillation. The deaths typically result from impact during sports, e.g., by being hit by a baseball, a puck, a softball, a lacrosse ball, or a hand, foot, or elbow (e.g., in martial arts). Efforts have been undertaken to mandate the use of chest protection for at-risk sports participants, such as baseball and lacrosse players. Assessing the effectiveness of chest wall protection necessitates the development of a model of commotion cordis to understand the mechanism and to evaluate preventive measures.